A. Technical Field
This invention relates generally to distributed multi-stage switching architectures, and more particularly, to intra-node fault recovery within a multi-stage switching architecture.
B. Background of the Invention
The importance of optical networking technology in today's society is well understood. Optical networks allow large amounts of information to be transmitted at high data rates across very long distances. The reliance on these networks by individuals and companies requires that the networks operate with minimal failures and lost data events.
In optical long haul scenarios, multiple channels or wavelengths are typically multiplexed together and inserted into a fiber optic cable that spans a long distance. The optical signal, comprising multiple wavelengths, propagates within the fiber optic cable until its destination is reached. This signal may then be demultiplexed and the individual wavelengths further processed.
Connections within an optical network may be provisioned by switching data at one or more switching nodes. The switching nodes receive data on one port and switch the data to a provisioned output port. Because of this switching capability between ports, these switching nodes may be intermediary devices in a large number of connections that form end-to-end circuits within the network.
A switching node contains a cross connect that is used to physically connect ports on the node. The cross-connect usually represents the most basic building block for constructing an end-to-end circuit. The actual connections between the ports are often provisioned across a cross connect by a user. A series of cross connect connections across multiple nodes that provides an end-to-end communication circuit is generally referred to as a sub-network connection.
FIG. 1 illustrates an exemplary sub-network connection formed by linking a set of network elements. The network elements comprise switching elements needed to switch data or voice between one of the input channel to one of the output channels. The sub-network connection links client end-1 110 to a client end-2 120 through the network nodes 131-137.
In case of a failure at any of the cross-connects within the sub-network connection, which may arise from a failure at a switching element in a particular network node, the entire connection is broken. Upon detection of such a failure, a new sub-network connection may be required so that data may once again be communicated between the transmitting and receiving ends. Typically, this newly established sub-network connection completely avoids the faulty network node entirely. For example, if a failure occurs on any of the switching elements in the network node 133, a new sub-network connection needs to be set up that avoids the faulty network node 133 completely. The new sub-network connection uses network node 139 to route around the faulty network node 133.
The failure recovery time and complexity may be significant because establishing the new sub-network connection involves setting up a series of new cross-connections through multiple networks nodes. This failure time and complexity may adversely affect the performance of the network and the clients thereon.